GFI and Service Disconnect

Reply

  #1  
Old 10-02-11, 07:59 AM
Member
Thread Starter
Join Date: Oct 2008
Location: USA
Posts: 29
GFI and Service Disconnect

I am running electrical to a detached garage.

1 circuit - 20 amps
3 light fixtures on 1 switch
1 exterior light on 1 switch (possibly adding a timer circuit)
4 duplex receptacles (1 will operate the overhead door)
Roughly 50 total feet of circuit will be run through 1/2" EMT.

I am trying to plan the wiring schematic and have a few questions:

When using a GFCI receptacle to supply ground fault protection to other receptacles, it is my understanding there is not really a maximum number of receptacles you can load on that first GFCI receptacle. Is this correct? Is this also true of loading light fixtures/switches onto a GFCI receptacle?

My other questions is, what is the maximum distance the service disconnect box can be from the point of entry, and must it be at a certain height? Or will this go by local codes?

Also, I am unsure of what type of disconnect box I can/should use. Is there a certain type that is required or recommended for the type of circuit I am running?

Finally, while I am thinking about it, do I need to use compression fittings for EMT in a detached garage? Or can I use set screw fittings? I was just going to use compression fittings in either case, but I figured I'd ask just so I know.

Thanks in advance!!
 
Sponsored Links
  #2  
Old 10-02-11, 08:42 AM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,213
Roughly 50 total feet of circuit will be run through 1/2" EMT
.

First things first. If the garage is detached, how will you run EMT to it? If you are running underground, you shouldn't use EMT. PVC conduit or heavywall galvanized steel conduit would be acceptable, but I would use a minimum of 3/4" PVC conduit and forget the heavywall.
 
  #3  
Old 10-02-11, 09:34 AM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,981
After Joe's question is answered, here are some more info.

Originally Posted by PaulyWally View Post
When using a GFCI receptacle to supply ground fault protection to other receptacles, it is my understanding there is not really a maximum number of receptacles you can load on that first GFCI receptacle. Is this correct? Is this also true of loading light fixtures/switches onto a GFCI receptacle?
Correct. 15 and 20 amp GFCI devices have a 20 amp feed through rating. For obvious reasons you can not exceed that.

Originally Posted by PaulyWally View Post
My other questions is, what is the maximum distance the service disconnect box can be from the point of entry, and must it be at a certain height? Or will this go by local codes?
Since this is not a service you can pretty much put it where ever you want. That being said you still have to have the proper clearances about the disconnect. Height can be no higher than 6'6".

Originally Posted by PaulyWally View Post
Also, I am unsure of what type of disconnect box I can/should use. Is there a certain type that is required or recommended for the type of circuit I am running?
The disconnect can be a simple as a two pole switch if you are running what Joe suggested as long as it is a 20 amp. Or you could install a small panel with no more that six circuit breakers or even as large as a full size panel with a main breaker.

Originally Posted by PaulyWally View Post
Finally, while I am thinking about it, do I need to use compression fittings for EMT in a detached garage? Or can I use set screw fittings? I was just going to use compression fittings in either case, but I figured I'd ask just so I know.
Compression fittings are not needed or required. You may use them if you wish.
 
  #4  
Old 10-02-11, 11:09 AM
Member
Thread Starter
Join Date: Oct 2008
Location: USA
Posts: 29
Originally Posted by CasualJoe View Post
.

First things first. If the garage is detached, how will you run EMT to it? If you are running underground, you shouldn't use EMT. PVC conduit or heavywall galvanized steel conduit would be acceptable, but I would use a minimum of 3/4" PVC conduit and forget the heavywall.
Yes, of course!

I was going to run either 3/4" or 1" PVC, and I was going to aim for a depth of 8". I was told (by an electrician) that 6" was the minimum for PVC. However, I was looking in the NEC, and if I am reading it correctly PVC must be at 18" for this type of circuit. Or I could run IMT or rigid at a minimum depth of 6".

I also have not found any NEC amendments in my city's building code. So I guess I'm going to go with one of those. Personally, I'm not thrilled about digging an 18"+ trench, but I also don't want to wrestle with rigid. We'll see how the digging goes.
 
  #5  
Old 10-02-11, 11:46 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 32,657
Incorrect information deleted.
 

Last edited by ray2047; 10-02-11 at 07:30 PM.
  #6  
Old 10-02-11, 04:35 PM
Member
Thread Starter
Join Date: Oct 2008
Location: USA
Posts: 29
Originally Posted by ray2047 View Post
That is correct. The exception is a 120v feed maximum 20a proteced by a GFCI breaker. That would be 12" minimum.

Using a multi wire circuit on a 2 pole GFCI breaker at the source panel you would need to bury the line only 12" and have two 120v 20 amp circuits.
Ah! So that is what column 4 in the NEC 300.5 means. I didn't think that column applied to my situation for a number of reasons, so I basically ignored it.

But that is awesome information, and I truly appreciate it! It's such a great help because digging was not going well. The trench is 8 feet away from a 50+ year old tree, and there is a large array of roots I'm going through. To make matters worse, I'm in the midwest and 12" is about where our wonderful mineral-rich clay starts. And a trench digger probably wouldn't help much because of roots and space constraints.

But I digress. Point is... thank you!! It helps a great deal and I wouldn't have seen that in the NEC on my own.

Moderator Edit: Information in quotes was incorrect. Source of quote deleted. See post below for correct information.
 

Last edited by ray2047; 10-02-11 at 07:33 PM.
  #7  
Old 10-02-11, 07:16 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,981
You can not run a multi-wire circuit and use column 4 for your burial depth. Voltage needs to be 120 volts or less. You would have 240 volts between the two hots. Therefore, you are limited to a single, 120 volt, 20 amp max, GFCI protected circuit if you only want to dig 12".
 
  #8  
Old 10-02-11, 08:11 PM
Member
Thread Starter
Join Date: Oct 2008
Location: USA
Posts: 29
Originally Posted by Tolyn Ironhand View Post
You can not run a multi-wire circuit and use column 4 for your burial depth.
Thanks for that correction. I am only running 1 hot anyway. So I didn't fully process that the previous information was not entirely correct. I saw the 120v max in column 4 and didn't think further on it cause that's all I was running.

But here's a question regarding this. Can I run a third wire for a 3-way switch (to control an exterior light from the house as well as the garage)? Technically the voltage will not exceed 120v, right? Or is there more to column 4 than I am interpreting?

I wasn't going to do this right now. But I was keeping it in mind in case I choose to add it in the future.
 
  #9  
Old 10-03-11, 06:02 AM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,981
Originally Posted by PaulyWally View Post
But here's a question regarding this. Can I run a third wire for a 3-way switch (to control an exterior light from the house as well as the garage)? Technically the voltage will not exceed 120v, right? Or is there more to column 4 than I am interpreting?I wasn't going to do this right now. But I was keeping it in mind in case I choose to add it in the future.
Correct. As long as it is not over 120 volts, AND has GFCI protection, you can bury it with the same circuit. If you feed it off another circuit from the house (which you will need another GFCI) it can only control outside lights on the garage. Which sounds like your plan anyway.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'